There are many features of plant seed ontogony that make it an excellent system for the study of regulatory aspects of eukaryotic developmental molecular biology. In our analysis of abundant mRNAs and proteins which characterize cotton embryogenesis and early germination, we have described at least 5 mRNA/protein subsets, each of which appears to be under a different regulatory regime. About 14 proteins become abundant in late embryogenesis and can be caused to appear prematurely in very young embryos by incubation with the hormone abscisic acid (ABA). The synthesis of this subset appears to be directly regulated at the steady state mRNA level and as such provides an excellent opportunity for the study of the regulation of coordinately expressed genes and of the molecular basis of hormone action. Our long term interests are to understand how the synthesis of these ABA induced proteins come to be regulated together and to understand the role they play in the regulation of cell metabolism and gene expression. Our aims here are to examine several basic aspects of this regulation. Specifically, are these proteins and their mRNAs all expressed coordinately in all developmental and physiological contexts in response to ABA and if they are a part of a larger set of functionally related proteins. The synthesis rates of these proteins and their mRNA concentration will be measured as a function of development and ABA level using two dimensional gel electrophoresis and nucleic acid hybridization with recombinant DNA clones. We will also investigate if there exist much less abundant proteins which may also be members of the same set by conduction hybridization experiments between mRNAs and cDNAs from selected tissues with different hormonal states. Finally, the level of regulation at which protein synthesis is coordinately regulated will be examined by determining the steady state concentration of mRNA sequences in polysomal, nonpolysomal, and nuclear RNAs under different hormonal regimes with recombinant DNA probes. Specifically, is there any relationship between the synthesis rates of these proteins and the steady state concentration of mRNA sequences in nuclear RNAs during the periods when the synthesis of these proteins are affected by changing hormone levels?